On examining the contents of images it has proven that detecting regions showing sudden changes of different kind, is a very important stage of the analysis. These regions are typically characterized in that one or several features within these regions, show certain specific conditions between different sub-regions. Such suddenly changing features can, for example, give rise to borders between sub-regions with different feature values. One typical case is a texture having features varying from one region to the other, which is described by a discontinuity in a vector field.
One on-going problem has been that descriptions of changes in vector fields have not been able, in a suitable way, to characterize both the changes of the direction and the changes of the magnitude of the vectors. For example it has not been possible with earlier equipment to detect variations of these feature vectors within certain angle regions. It has therefore been difficult to distinguish between regions of certain types if these regions have been characterized by vectors of these directions. Attempts to overcome this problem have centered around efforts in areas relating to computerized image analysis and in particular to methods which have been implemented by means of a program for use with a general purpose computer. However, such methods have been inherently slow.
The present invention concerns an apparatus for distinguishing sub-regions characterized by vectors that differ either in direction or magnitude, or in combination thereof with high speed and reliability.